In practice, assemblies for conveying stacked documents along a particular conveying path in a conveying direction are typically provided with a circulating conveying surface having a section extending along the conveying path and with a conveyor roller which is suspended opposite the section of the circulating conveying surface for reciprocating movement between positions at different distances from that section of the circulating conveying surface and in operating condition exerts a press-on force in the direction of that section of the circulating conveying surface, and a transmission for driving the conveyor roller with a couple in the conveying sense, which couple causes the conveyor roller to rotate in operation in such a manner that a circumferential section of the conveyor roller facing the above-mentioned section of the conveying surface is moved in the conveying direction.
In conveying a stack of documents, the problem occurs that when the stack is brought between a conveyor roller and a conveying surface, an irregularity in the conveyance occurs each time the conveyor roller, or at least a belt extending around the conveyor roller, butts against the leading edge of the stack. More particularly, a shock load is produced, which is stronger according as the stack is thicker.
Further, the documents stacked onto each other are shifted relative to each other in the conveying direction. Stacked documents that have shifted relative to each other in the conveying direction are difficult to process further. If the next operation consists, for instance, in inserting the documents into an envelope, the chances of problems are increased, because the total length of the stack in the conveying direction has increased and the documents must, at least partly, shift back relative to each other again so as to allow closure of the envelope with the documents inserted therein. Owing to increased relative friction of the documents brought between the walls of the envelope, alignment or re-alignment of documents in the envelope is relatively unreliable.
If the next operation consists, for instance, in the folding of the stack of documents, only a very slight relative shift of the supplied documents gathered into a stack can be accepted, because the relative shift can no longer be undone after a fold in a direction transverse to the conveying direction has been provided.